This invention relates generally to automatic door control systems for moveable doors and more particularly to the use of pulse width modulation for controlling the door motor.
Typical automatic door control systems require a means for sensing the position of the door. This position sensing is used for controlling the various stages of operation of the door and for monitoring the door for abnormal operation, such as an obstructed door. Position monitoring devices are used such as limit switches, which are useful for monitoring specific positions of the door, but do not monitor for non-movement indicating that the door is obstructed.
Some prior art automatic door control systems use multitap autotransformers (with multiple fixed speeds) for motor speed control. This can cause the door to jerk when changing speeds.
The foregoing illustrates limitations known to exist in present automatic door control systems. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.